Question: Simplify the following expression: $q = \dfrac{2x}{5} + \dfrac{9x}{4}$
Solution: In order to add expressions, they must have a common denominator. The smallest common denominator is the least common multiple of $5$ and $4$ $\lcm(5, 4) = 20$ $ q = \dfrac{4}{4} \cdot \dfrac{2x}{5} + \dfrac{5}{5} \cdot \dfrac{9x}{4} $ $q = \dfrac{8x}{20} + \dfrac{45x}{20}$ $q = \dfrac{8x +45x}{20}$ $q = \dfrac{53x}{20}$